The present invention relates to a magneto-optical disk apparatus and a position adjustment method of a head mechanism which is mounted in the magneto-optical disk apparatus. More particularly, the present invention relates to the magneto-optical disk apparatus which is preferable to improvement of a recording frequency and the position adjustment method of a head mechanism which is arranged to adjust a relative position of a magnetic head against an optical head, both of which heads are mounted in the magneto-optical disk apparatus.
Like a magnetic disk such as a floppy disk, the magneto-optical disk has been heretofore put into practice as an information recording medium from or on which information may be repetitively recorded, reproduced and erased. This magneto-optical disk is arranged to magnetically record data on a magnetic layer by virtue of an external magnetic field with heat caused by a laser beam. The magneto-optical disk apparatus for this type of magneto-optical disk generally includes an optical head for focusing a laser beam as a beam spot on the magnetic layer of the magneto-optical disk and a magnetic head for applying an external magnetic field onto the magnetic layer, the magnetic head located as opposed to the optical head.
The laser beam spot applied onto the magnetic layer has a diameter of 1 to 3 xcexcm, while the main magnetic pole composing the magnetic head is sized to be as large as 100 to 300 xcexcm. In this composition, it has been enough to position the magnetic head in the specific range of the laser beam target section where the necessary magnetic field for recording or erasing information may be applied without having to strictly match the axial center of the main magnetic pole to the optical axis of the optical head.
Hereafter, the description will be oriented to the construction of the head mechanism of the conventional magnetic-optical disk apparatus and the adjustment method of the magnetic head against the optical axis of the optical head with reference to FIGS. 7A and 7B showing the plan view and the front view.
As shown in FIGS. 7A and 7B, the optical head 1 is mounted at one tip of an arm 3 formed in a horseshoe manner and the magnetic head 2 is mounted at the other tip of an arm 3. The optical head 1 is opposed to the magnetic head 2. The optical head 1 is secured to a lower arm 3a with an objective lens 1a directed upward. The objective lens 1a provides an actuator (not shown) for auto-focusing and tracking control. By operating the actuator, it is possible to properly change the position of the laser beam spot. On the other hand, the magnetic head 2 is mounted on a slider 4. The slider 4 is mounted on the upper end of the arm 3 with a gimbal spring 5 laid therebetween.
The gimbal spring 5 is fixed on the upper end of the arm 3 by means of a screw 6. The gimbal spring 5 has a through hole 5a whose diameter is far larger than that of the screw 6. Hence, a larger washer (not shown) than the through hole 5a is fitted into the through hole 5a. Before fastening the screw, the setting position of the magnetic head 2 against the optical head (more strictly, the objective lens 1a) may be adjusted in the allowance range. Further, the arm 3 is linearly moved in the radial direction of the magneto-optical disk 7 by means of the driving device (not shown). Or, the arm 3 is driven arcuately so that the head setting section is moved substantially in the radial direction of the magneto-optical disk 7 with the arm end linked at the given position of the magneto-optical disk apparatus as a supporting point.
In this construction, the adjustment of the setting position of the magnetic head 2 is carried out by mounting the magneto-optical disk 7 to the magneto-optical disk apparatus and repeating the recording of information on the magneto-optical disk 7 and the reproduction of information therefor. That is, when the assembly of the magneto-optical disk apparatus is terminated, the magneto-optical disk 7 is mounted to the magneto-optical disk apparatus so that the magnetic head 2 operates to generate a magnetic field of a predetermined recording intensity as the optical head 1 is applying a laser beam of a recording intensity, for recording information on the magneto-optical disk 7. Next, the drive of the magnetic head 2 is stopped and then the intensity of the laser beam applied from the magneto-optical disk 7 is switched into a reproducing intensity on which the recorded information is reproduced. If the output of the reproduction signal detected by the optical head 1 does not reach a predetermined value, it is grasped that the external magnetic field of the predetermined intensity is not applied to the magnetic layer because of the improper setting position of the magnetic head 2. Then, the mounting location of the gimbal spring 5 against the upper arm 3b is changed by loosening the screw 6. Until the reproduction signal reaches the output of the predetermined value or more, the foregoing operations are repeated.
In the field of the magneto-optical recording, one of the most significant technical issues is improvement of a recording frequency. For improving the recording frequency, it is indispensable to reduce the magnetic head 2 in size. The reduced magnetic head 2 leads to narrowing the distribution of a magnetic field generated by the magnetic pole, which needs to more precisely position the magnetic head 2 against the optical axis of the optical head.
However, the conventional mechanism for adjusting the position of the magnetic head does not provide a fine adjustment mechanism for the magnetic head. It means that the conventional adjustment mechanism has difficulty in positioning the magnetic head 2 against the optical axis of the optical head with precision, so that the position adjustment of the magnetic head is not made high-efficient. Moreover, the foregoing conventional adjustment method of the magnetic head needs to actually record information on the magneto-optical disk, which may suffer from erroneous erasion of information to be saved.
The present invention is made to overcome the foregoing difficulties, and it is an object of the present invention to provide a magneto-optical disk apparatus and an adjustment method of a head mechanism which are arranged to strictly and quickly adjust the setting position of a magnetic head against an optical axis of an optical head.
In order to overcome the foregoing difficulties, according to the invention, at first, a magneto-optical disk apparatus for locating an optical head for focusing a laser beam as a beam spot on a magnetic layer of each side of the magneto-optical disk as opposed to the magnetic head for applying an external magnetic field on the magnetic layer is constructed to provide a fine adjustment mechanism for adjusting the setting position of the magnetic head against the optical axis of the optical head in an arm mechanism for holding the magnetic head.
As the fine adjustment mechanism, there may be considered a member containing a gimbal spring in parallel to the magnetic head and the slider is slidably mounted with the arm mechanism so that the member may be slid by the arm mechanism. This type of fine adjustment mechanism of the magnetic head allows the magnetic head to move in the desired direction step by step. Hence, this type of fine adjustment mechanism enables to adjust the setting position of the magnetic head against the optical axis of the optical head more quickly and precisely than the conventional adjustment mechanism in which the setting position of the magnetic head is changed by using a clearance of the screw through hole opened in the gimbal spring.
Second, like the above, the magneto-optical disk apparatus is constructed to mount a plurality of magnetic heads adjacently to one slider and provide a head driving device for individually driving these magnetic heads.
The mount of these magnetic heads adjacent to one slider allows the magnetic head to be set to the position at which the most excellent recording and reproducing characteristics are made fully effective without having to adjust those magnetic heads one by one. This mount therefore makes the assembly or maintenance of the magneto-optical disk apparatus easier.
Third, like the above, the magneto-optical disk apparatus is constructed to provide a photo detector for detecting a laser beam applied by the optical head and passed through the magneto-optical disk in the magnetic head or the slider for holding the magnetic head.
In this construction, the photo detector is mounted on the disk-opposed side of the magnetic head or the slider so that a light acceptance plane is directed to the disk plane of the magneto-optical disk for the purpose of directly detecting the laser beam passed through the magneto-optical disk. Or, the photo detector is mounted at any location of the magnetic head or the slider so that the light acceptance plane is directed in any direction, for the purpose of detecting the beam entered into an optical fiber located on the disk-opposed plane of the magnetic head or the slider and passed through the magneto-optical disk
In order to enhance the intensity of the reflected light, a reflection layer made of metal or the like is generally laminated on a magnetic layer of the magneto-optical disk. However, if the magneto-optical disk contains a reflection layer, about several percents of laser beam for recording and reproduction is passed through the reflection layer. Hence, by providing the photo detector in the magnetic head or the slider and detecting the light passed through the magneto-optical disk, it is possible to derive the relative position of the magneto-optical disk of the laser beam spot against the magnetic head, for the purpose of facilitating the adjustment of the setting position of the magnetic head.
It goes without saying that the magneto-optical disk apparatus provided with the photo detector may have a fine adjustment mechanism for adjusting the setting position of the magnetic head against the optical axis of the optical head.
On the other hand, an adjustment method of a setting position of a magnetic head against an optical axis of an optical head, at first, comprises the steps of mounting a magneto-optical disk having a magnetic layer for reversing the direction of magnetization toward an external magnetic field when the external magnetic field of a given intensity is applied onto the magneto-optical disk as applying the laser beam of the reproduction level thereon in the magneto-optical disk apparatus provided with an optical disk and a magnetic disk, applying the external magnetic head from the magnetic field as applying the laser beam of the reproduction level onto the magneto-optical disk, detecting the output of the reproduction signal from a signal reproducing section provided in the magneto-optical disk apparatus concurrently with the application of the magnetic field, and changing the setting position of the magnetic head against the optical axis of the optical head so that the output of the reproduction signal is made maximum about the direction of the external magnetic field.
The magneto-optical disk may be a magnetic super resolution type disk. The magnetic super resolution type magneto-optical disk provides three magnetic layers, that is, a recording layer, a cutting layer and a reproducing layer. When the laser beam of the reproduction level is applied onto the magneto-optical disk, the magnetization of the cutting layer is cancelled so that the recording layer is magnetically independent of the reproduction layer. By applying the external magnetic field, therefore, the magnetizing direction of the reproduction layer is inverted toward the external magnetic field. The highest magnetization of the reproduction layer takes place at the main magnetic pole of the magnetic head, so that the output of the reproduction signal from the optical head is proportional to the magnitude of the magnetization of the reproduction layer. Hence, by adjusting the setting position of the magnetic head so that the reproduction signal output is made maximum about the direction of the external magnetic field, whatever the main magnetic pole of the magnetic head may be reduced in size, it is possible to precisely oppose the main magnetic pole of the magnetic head to the optical axis of the optical head, thereby quickly and precisely adjusting the setting position of the magnetic head.
In this construction, the setting position of the magnetic head may be changed by operating the fine adjustment mechanism provided in the arm mechanism for holding the magnetic head. When determining the setting position of the magnetic head, after specifying the position at which the reproduction signal output is made maximum about the direction of the external magnetic field, preferably the actuator for tracking control provided in the optical head is operated for scanning a laser beam spot equally on an inner peripheral side and an outer peripheral side with the target track from which the reproduction signal output is detected as a center and for keeping the maximum reproduction signal output about the direction of the external magnetic field over a given scan width. By this operation, it is possible to easily know whether or not the peak of the external magnetic field (that is not an acute peak but a stable area according to the magnitude of the magnetic pole) matches to the center of the track from which the reproduction signal output is detected. This allows the setting position of the magnetic head to be adjusted more precisely.
Second, like the above, the adjustment method of a head mechanism comprises the steps of mounting to the magneto-optical disk apparatus having an optical head and a plurality of magnetic heads mounted to the slider a magneto-optical disk having the magnetic layer for reversing the direction of magnetization toward the external magnetic field when the external magnetic field of a given intensity is applied as applying the laser beam of a reproduction level, applying the external magnetic field sequentially from the magnetic heads as applying the laser beam of the reproduction level onto the magneto-optical disk, detecting a reproduction signal output from a signal reproduction section provided in the magneto-optical disk apparatus concurrently with the application of the magnetic field, and selecting the magnetic head for keeping the reproduction signal output maximum about the direction of the external magnetic field.
The foregoing method does not need the movement operation of the magnetic head, so that the setting position of the magnetic head may be more easily adjusted.
Third, the adjustment method of a head mechanism comprises the steps of mounting a magneto-optical disk to a magneto-optical disk apparatus having an optical head and a magnetic head and a photo detector for detecting a laser beam applied by the optical head onto the magnetic head or a slider for holding the magnetic head and passed through the magneto-optical disk, detecting an output signal of the photo detector as applying a laser beam of a reproduction level onto the magneto-optical disk, and changing the setting position of the magnetic head against the optical axis of the optical head as keeping the output signal at a given level.
The foregoing method does not need to rotatively drive the magneto-optical disk and detect the reproduction signal output, which enables to more easily adjust the setting position of the magnetic head. In this aspect of the invention, the setting position of the magnetic head may be changed by operating the fine adjustment mechanism provided in the arm mechanism for holding the magnetic head.